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Sounding the Siren
Times are tough for Florida’s manatees
Manatees are no strangers to hardship—and so far this year they’ve gotten no breaks.
More than 600 manatees have already died in 2013 as of early June—more than 10 percent of Florida’s population. In fact, in just the first three months of 2013, the death tally exceeded that of last year’s total.
“This number is alarmingly high and should give the U.S. Fish and Wildlife Service pause as it considers a proposal to change the status of the manatee from an endangered species to a threatened one,” says Elizabeth Fleming, Defenders’ Florida representative.
Members of the scientific order Sirenia, these sirens of the sea face their biggest threat from boat strikes and habitat destruction. But this year’s harmful algal bloom—called red tide because often the water turns crimson—has significantly added to their woes.
Red tides are natural, seasonal occurrence off Florida’s Gulf Coast caused by higher than normal concentrations of microscopic algae. These plantlike organisms produce toxins that affect the central nervous systems of animals and make it difficult for them to breathe. The bloom’s trigger remains unclear and its scale depends on factors like water temperature and weather. But nutrients from agricultural runoff can also feed the algae and make blooms more intense if wind and ocean currents draw them to the coastline. This recent outbreak persisted from September to mid April, making it the worst since 1996.
Manatees are affected by red tide neurotoxins mainly because they feed on algae-coated sea grass. They also can inhale them when they breathe. The toxins can cause seizures, impair coordination and ability to float, and prevent manatees from lifting their snouts above the water to breathe. The result is death by drowning. Swimming manatees must surface for air about every three to five minutes. At rest, they can hold their breath for up to 20 minutes.
“Even though we’ve seen the worst of this year’s red tide in southwest Florida, manatees will continue to be affected for some time because the neurotoxins have settled onto seagrass beds,” says Fleming. “And we don’t know yet how this will affect the population over the long term.”
Meanwhile, on the east side of Florida an unknown culprit is killing more manatees. About 100 have perished since last July. The cause could be a different toxin found in food manatees may have been forced to eat after 99 percent of their sea grass staple died off in some areas, most likely from a combination of unusually cold temperatures and drought.
Roll these factors together with the major human cause of manatee deaths—recreational boat strikes—and it’s clear that the manatee’s future is far from secure.
Since record-keeping began in 1974, more than 40 percent of manatee deaths were human-caused, with more than 34 percent from run-ins with watercraft hulls and propellers. So far this year, boat strikes have already killed 26 of these slow-moving, gentle creatures.
To help manatees survive, Defenders is working to protect important manatee habitat and has successfully advocated for the creation of more slow-speed zones and improved enforcement. Defenders also supported the acquisition of Three Sisters Spring in the Crystal River National Wildlife Refuge, the establishment of the Kings Bay Manatee Refuge, and the strengthening of sea grass protections in Everglades National Park.
“With only about 5,000 animals left, we have our work cut out for us,” says Fleming. “I am hopeful the population will rebound and manatees will one day no longer need ESA protections. Until then, we remain adamant in ensuring their protection.”
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October 25, 2016 | 10.55 AM
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